Vagus Branches in the Thorax

Mnemonic

“Left goes anterior, right goes posterior” at the oesophagus, following the embryonic 90 degree clockwise rotation of the stomach:

• Left vagus becomes the anterior gastric nerve
• Right vagus becomes the posterior gastric nerve

“LARP”: Left Anterior, Right Posterior.

Their thoracic branches:

• Left recurrent laryngeal, hooking under the aortic arch at the ligamentum arteriosum
• Right recurrent laryngeal, hooking under the right subclavian artery in the neck
• Cardiac branches to the cardiac plexus
• Pulmonary branches, forming the plexus behind the lung root, while the phrenic nerve passes in front of it

“Phrenic in front of the hilum, vagus behind” is the relation most often examined.

The rotation rule matters surgically: a highly selective vagotomy must preserve the nerves of Latarjet to the antrum while dividing the acid-secreting branches.

Expansion

• Recurrent laryngeal - on the left only, hooking under the aortic arch at the ligamentum arteriosum
• Cardiac branches - to the cardiac plexus, slowing rate and conduction
• Pulmonary branches - to the anterior and posterior pulmonary plexuses; bronchoconstriction and increased secretion
• Oesophageal branches - forming the oesophageal plexus, which reconstitutes as the anterior and posterior vagal trunks

The right vagus descends alongside the trachea and passes behind the right lung root; the left crosses the aortic arch, medial to the phrenic nerve, and passes behind the left lung root.

A useful contrast to hold: the vagus passes behind the lung root and the phrenic in front, and the vagus is parasympathetic while the sympathetic supply comes from the chain on the rib heads.